The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Generally, a seat for a vehicle is configured to slidably move in forward/rearward directions of a vehicle by using a seat rail. As shown in FIGS. 1 to 4B, the seat rail extends in the forward/rearward directions and includes a fixed rail 1 provided to be fixed to a floor panel in the vehicle and a moving rail 2 combined with the fixed rail 1 to slidably move along a longitudinal direction of the fixed rail 1.
Furthermore, the seat rail includes a locking apparatus so as to restrict movement of the moving rail 2 in the forward/rearward directions. The locking apparatus includes an electric-powered type operated by power of a motor and a manual type manipulated by a user.
As a kind of a manual type, a locking pin type realizing a more precise operation as multiple locking pins operate independently, as shown in the drawings, includes a locking mounting bracket 3, a release lever 4, a lever shaft 5, a lever spring 6, a guide bracket 7, multiple locking pins 8, and one locking pin spring 9 provided per each of the locking pins 8.
The locking mounting bracket 3 is combined on an upper surface of the moving rail 2 so as to be fixed thereto and includes opposing bracket flanges 3a provided thereon when the locking mounting bracket 3 is combined with the moving rail 2, the bracket flanges protruding from an outer side of the moving rail 2 in a side direction thereof and being spaced apart from each other in the forward/rearward directions.
The release lever 4 is positioned between the bracket flanges 3a, wherein the lever shaft 5 integrally passes through the opposing bracket flanges 3a and the release lever 4 in the forward/rearward directions and is combined therewith, and the lever spring 6 is wound on the lever shaft 5, a first end of the lever spring 6 being supported by the locking mounting bracket 3 and a second end thereof being supported by the release lever 4.
The release lever 4 includes a manipulation part 4a and an operation part 4b contacting with the locking pin 8. The manipulation part 4a protruding to an outer side of the seat rail relative to the lever shaft 5 is manipulated by a worker. The operation part 4b passes through the moving rail 2, and an end portion of the operation part 4b is positioned in the moving rail 2, and contacts with the locking pin 8 so as to move the locking pin 8 during the manipulation of the manipulation part 4a. 
When a user presses down the release lever 4, the lever spring 6 is compressed, and when the release lever 4 being pressed down is released, the release lever 4 is restored to an initial position thereof by a restoring force of the lever spring 6.
The guide bracket 7 is an L-shaped bracket, a first end thereof being combined with an inner side surface of one side portion of the moving rail 2 so as to be fixed thereto and a second thereof being provided so as to pass through an inner space of the moving rail 2 in leftward/rightward directions of the seat rail.
The multiple locking pins 8 are arranged in a row in the forward/rearward directions, and each of the locking pins 8 is provided to integrally pass through the fixed rail 1, the guide bracket 7, the moving rail 2, and the locking mounting bracket 3 in a vertical direction and to move vertically. Opposite ends of the locking pin spring 9 are provided to be supported by the retainer 10 and a locking pin flange 8a. 
The retainer 10 is provided on an inner side of the upper surface of the moving rail 2, and the locking pin flange 8a is provided to be integral to the locking pin 8.
However, as for a conventional seat rail, each of the bracket flanges 3a with which the lever shaft 5 is combined is cut on a side thereof in an upward direction so as to have an open hole 3b. Though the open hole 3b is configured to combine the lever shaft 5 with the bracket flange 3a, shaking of the release lever 4 increases due to the open hole 3b during the manipulation of the release lever 4, and as the shaking of the release lever 4 increases, the operability of the locking pin 8 deteriorates.
In addition, the moving rail 2 includes a window 11 provided on one side wall 2a thereof, and the operation part 4b of the release lever 4 is provided by passing through the window 11. As for the conventional seat rail, as a lower surface of the operation part 4b directly contacts with a lower surface 11a of the window 11 during manipulation of the release lever 4, a contact section is widely distributed, whereby operational noise is loud.
As shown in FIG. 1, when the manipulation part 4a of the release lever 4 is pressed down and released, the release lever 4 is restored to the initial position thereof as shown in FIG. 1 by the restoring force of the lever spring 6. In this case, the lower surface of the operation part 4b of the release lever 4 directly contacts with the lower surface 11a of the window 11 and noise occurs.
A reference number D1 shown in FIGS. 4A to 4B is a horizontal width of the operation part 4b, and as the entirety of the horizontal width D1 of the operation part 4b directly contacts with the lower surface 11a of the window 11, the contact section is widely distributed, and a loud operational noise occurs.
Furthermore, the second end of the lever spring 6 is configured to be supported by the release lever 4, and the conventional release lever 4 does not have a structure which the second end of the lever spring 6 is held in and fixed to. Accordingly, since the release lever 4 cannot be stably provided by the lever spring 6, the shaking of the release lever 4 increases during the manipulation of the release lever 4, and as the shaking of the release lever 4 increases, operability of the locking pin 8 deteriorates.